This proposal will combine the expertise of two groups of investigators -- an active program performing clinical intervention trials to treat rheumatoid arthritis and a group of immunopathologists with new developed techniques to analyze cytokine and other key molecules in inflammatory tissue. Synovial tissue will be obtained using needle arthroscopy with visually directed biopsies before and after therapy with several biologic agents and the tissue thoroughly evaluated using a combined analysis of immunohistochemistry, in situ hybridization, an quantitative competitive reverse transcript/PCR (QC-RT-PC). Cytokine expression will also be determined by ELISA technique in synovial fluid obtained at the same time as the synovial biopsy. The central focus of this application is to examine two hypotheses concerning the pathophysiology of inflammatory synovitis in rheumatoid arthritis -- that continual local activation of T cells to produce Th1-like cytokines is the key mechanism to maintain chronicity in synovitis and that TNFalpha is the primary effector of local inflammatory changes. Although some analysis of synovial fluid specimens will be performed, the emphasis will be on examining the effects of these biologics on synovial tissue, using the complementary techniques of in situ hybridization, monoclonal antibody based immunohistochemical analysis, and a novel approach to QC-RT- PCR. Since most clinical trials of biologics have shown heterogenous responses among individual patients, the immunophenotypic pattern of lesions prior to treatment associated with clinical treatment response and the specific molecular changes within inflammed synovium that accompany clinical improvement will be documented.